Steven Rostedt 327e286643 fgraph: Do not enable function_graph tracer when setting funcgraph-args ... When setting the funcgraph-args option when function graph tracer is net enabled, it incorrectly enables it. Worse, it unregisters itself when it was never registered. Then when it gets enabled again, it will register itself a second time causing a WARNing. ~# echo 1 > /sys/kernel/tracing/options/funcgraph-args ~# head -20 /sys/kernel/tracing/trace # tracer: nop # # entries-in-buffer/entries-written: 813/26317372 #P:8 # # _-----=> irqs-off/BH-disabled # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | <idle>-0 [007] d..4. 358.966010: 7) 1.692 us | fetch_next_timer_interrupt(basej=4294981640, basem=357956000000, base_local=0xffff88823c3ae040, base_global=0xffff88823c3af300, tevt=0xffff888100e47cb8); <idle>-0 [007] d..4. 358.966012: 7) | tmigr_cpu_deactivate(nextexp=357988000000) { <idle>-0 [007] d..4. 358.966013: 7) | _raw_spin_lock(lock=0xffff88823c3b2320) { <idle>-0 [007] d..4. 358.966014: 7) 0.981 us | preempt_count_add(val=1); <idle>-0 [007] d..5. 358.966017: 7) 1.058 us | do_raw_spin_lock(lock=0xffff88823c3b2320); <idle>-0 [007] d..4. 358.966019: 7) 5.824 us | } <idle>-0 [007] d..5. 358.966021: 7) | tmigr_inactive_up(group=0xffff888100cb9000, child=0x0, data=0xffff888100e47bc0) { <idle>-0 [007] d..5. 358.966022: 7) | tmigr_update_events(group=0xffff888100cb9000, child=0x0, data=0xffff888100e47bc0) { Notice the "tracer: nop" at the top there. The current tracer is the "nop" tracer, but the content is obviously the function graph tracer. Enabling function graph tracing will cause it to register again and trigger a warning in the accounting: ~# echo function_graph > /sys/kernel/tracing/current_tracer -bash: echo: write error: Device or resource busy With the dmesg of: ------------[ cut here ]------------ WARNING: CPU: 7 PID: 1095 at kernel/trace/ftrace.c:3509 ftrace_startup_subops+0xc1e/0x1000 Modules linked in: kvm_intel kvm irqbypass CPU: 7 UID: 0 PID: 1095 Comm: bash Not tainted 6.16.0-rc2-test-00006-gea03de4105d3 #24 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:ftrace_startup_subops+0xc1e/0x1000 Code: 48 b8 22 01 00 00 00 00 ad de 49 89 84 24 88 01 00 00 8b 44 24 08 89 04 24 e9 c3 f7 ff ff c7 04 24 ed ff ff ff e9 b7 f7 ff ff <0f> 0b c7 04 24 f0 ff ff ff e9 a9 f7 ff ff c7 04 24 f4 ff ff ff e9 RSP: 0018:ffff888133cff948 EFLAGS: 00010202 RAX: 0000000000000001 RBX: 1ffff1102679ff31 RCX: 0000000000000000 RDX: 1ffffffff0b27a60 RSI: ffffffff8593d2f0 RDI: ffffffff85941140 RBP: 00000000000c2041 R08: ffffffffffffffff R09: ffffed1020240221 R10: ffff88810120110f R11: ffffed1020240214 R12: ffffffff8593d2f0 R13: ffffffff8593d300 R14: ffffffff85941140 R15: ffffffff85631100 FS: 00007f7ec6f28740(0000) GS:ffff8882b5251000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7ec6f181c0 CR3: 000000012f1d0005 CR4: 0000000000172ef0 Call Trace: <TASK> ? __pfx_ftrace_startup_subops+0x10/0x10 ? find_held_lock+0x2b/0x80 ? ftrace_stub_direct_tramp+0x10/0x10 ? ftrace_stub_direct_tramp+0x10/0x10 ? trace_preempt_on+0xd0/0x110 ? __pfx_trace_graph_entry_args+0x10/0x10 register_ftrace_graph+0x4d2/0x1020 ? tracing_reset_online_cpus+0x14b/0x1e0 ? __pfx_register_ftrace_graph+0x10/0x10 ? ring_buffer_record_enable+0x16/0x20 ? tracing_reset_online_cpus+0x153/0x1e0 ? __pfx_tracing_reset_online_cpus+0x10/0x10 ? __pfx_trace_graph_return+0x10/0x10 graph_trace_init+0xfd/0x160 tracing_set_tracer+0x500/0xa80 ? __pfx_tracing_set_tracer+0x10/0x10 ? lock_release+0x181/0x2d0 ? _copy_from_user+0x26/0xa0 tracing_set_trace_write+0x132/0x1e0 ? __pfx_tracing_set_trace_write+0x10/0x10 ? ftrace_graph_func+0xcc/0x140 ? ftrace_stub_direct_tramp+0x10/0x10 ? ftrace_stub_direct_tramp+0x10/0x10 ? ftrace_stub_direct_tramp+0x10/0x10 vfs_write+0x1d0/0xe90 ? __pfx_vfs_write+0x10/0x10 Have the setting of the funcgraph-args check if function_graph tracer is the current tracer of the instance, and if not, do nothing, as there's nothing to do (the option is checked when function_graph tracing starts). Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/20250618073801.057ea636@gandalf.local.home Fixes: c7a60a733c ("ftrace: Have funcgraph-args take affect during tracing") Closes: https://lore.kernel.org/all/4ab1a7bdd0174ab09c7b0d68cdbff9a4@huawei.com/ Reported-by: Changbin Du <changbin.du@huawei.com> Tested-by: Changbin Du <changbin.du@huawei.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>		2025-06-18 07:43:22 -04:00
..
rv	rv: Fix out-of-bound memory access in rv_is_container_monitor()	2025-04-12 12:13:30 -04:00
Kconfig	ftrace: Have tracing function args depend on PROBE_EVENTS_BTF_ARGS	2025-04-02 09:50:56 -04:00
Makefile	…
blktrace.c	traceevent/block: Add REQ_ATOMIC flag to block trace events	2025-05-23 09:18:48 -06:00
bpf_trace.c	bpf: Fix error return value in bpf_copy_from_user_dynptr	2025-05-23 13:25:02 -07:00
bpf_trace.h	…
error_report-traces.c	…
fgraph.c	ftrace: Show subops in enabled_functions	2025-05-08 09:36:08 -04:00
fprobe.c	tracing: fprobe: Fix RCU warning message in list traversal	2025-05-10 08:28:02 +09:00
ftrace.c	RISC-V Patches for the 6.16 Merge Window, Part 1	2025-06-06 18:05:18 -07:00
ftrace_internal.h	…
kprobe_event_gen_test.c	…
pid_list.c	tracing: Cleanup upper_empty() in pid_list	2025-05-14 11:19:32 -04:00
pid_list.h	…
power-traces.c	…
preemptirq_delay_test.c	…
rethook.c	…
ring_buffer.c	ring-buffer: Fix buffer locking in ring_buffer_subbuf_order_set()	2025-06-06 20:25:55 -04:00
ring_buffer_benchmark.c	…
rpm-traces.c	…
synth_event_gen_test.c	…
trace.c	ring-buffer changes for v6.16:	2025-05-30 21:20:11 -07:00
trace.h	tracing: Allow the top level trace_marker to write into another instances	2025-05-09 15:19:11 -04:00
trace_benchmark.c	…
trace_benchmark.h	…
trace_boot.c	…
trace_branch.c	tracing: branch: Use trace_tracing_is_on_cpu() instead of "disabled" field	2025-05-09 15:19:10 -04:00
trace_btf.c	…
trace_btf.h	…
trace_clock.c	…
trace_dynevent.c	tracing: probes: Fix a possible race in trace_probe_log APIs	2025-05-13 22:23:34 +09:00
trace_dynevent.h	tracing: probes: Fix a possible race in trace_probe_log APIs	2025-05-13 22:23:34 +09:00
trace_entries.h	ftrace: Expose call graph depth as unsigned int	2025-05-08 09:36:08 -04:00
trace_eprobe.c	tracing: add missing trace_probe_log_clear for eprobes	2025-05-10 08:44:50 +09:00
trace_event_perf.c	…
trace_events.c	tracing: Add a helper function to handle the dereference arg in verifier	2025-05-09 15:19:11 -04:00
trace_events_filter.c	tracing: Do not free "head" on error path of filter_free_subsystem_filters()	2025-06-10 09:39:58 -04:00
trace_events_filter_test.h	…
trace_events_hist.c	tracing: Rename event_trigger_alloc() to trigger_data_alloc()	2025-05-09 15:19:11 -04:00
trace_events_inject.c	…
trace_events_synth.c	tracing: Do not add length to print format in synthetic events	2025-04-09 11:34:21 -04:00
trace_events_trigger.c	tracing updates for v6.16:	2025-05-29 21:04:36 -07:00
trace_events_user.c	…
trace_export.c	…
trace_fprobe.c	Probes fixes for v6.14:	2025-04-08 12:51:34 -07:00
trace_functions.c	tracing updates for v6.16:	2025-05-29 21:04:36 -07:00
trace_functions_graph.c	fgraph: Do not enable function_graph tracer when setting funcgraph-args	2025-06-18 07:43:22 -04:00
trace_hwlat.c	…
trace_irqsoff.c	tracing: Use atomic_inc_return() for updating "disabled" counter in irqsoff tracer	2025-05-09 15:19:10 -04:00
trace_kdb.c	tracing: kdb: Use tracer_tracing_on/off() instead of setting per CPU disabled	2025-05-09 15:18:47 -04:00
trace_kprobe.c	tracing: probes: Fix a possible race in trace_probe_log APIs	2025-05-13 22:23:34 +09:00
trace_kprobe_selftest.c	…
trace_kprobe_selftest.h	…
trace_mmiotrace.c	tracing/mmiotrace: Remove reference to unused per CPU data pointer	2025-05-08 09:36:09 -04:00
trace_nop.c	…
trace_osnoise.c	tracing/osnoise: Allow arbitrarily long CPU string	2025-05-08 09:36:09 -04:00
trace_output.c	tracing: Show preempt and irq events callsites from the offsets in field print	2025-05-06 11:34:52 -04:00
trace_output.h	…
trace_preemptirq.c	…
trace_printk.c	…
trace_probe.c	tracing: probes: Fix a possible race in trace_probe_log APIs	2025-05-13 22:23:34 +09:00
trace_probe.h	tracing: probe-events: Log error for exceeding the number of arguments	2025-03-27 21:19:54 +09:00
trace_probe_kernel.h	…
trace_probe_tmpl.h	…
trace_recursion_record.c	…
trace_sched_switch.c	…
trace_sched_wakeup.c	tracing: Convert the per CPU "disabled" counter to local from atomic	2025-05-09 15:19:10 -04:00
trace_selftest.c	…
trace_selftest_dynamic.c	…
trace_seq.c	…
trace_stack.c	tracing updates for v6.16:	2025-05-29 21:04:36 -07:00
trace_stat.c	…
trace_stat.h	…
trace_synth.h	…
trace_syscalls.c	…
trace_uprobe.c	bpf-next-6.16	2025-05-28 15:52:42 -07:00
tracing_map.c	…
tracing_map.h	…